This invention relates to exercise apparatus, and primarily to protection of the user against possible injury due to failure of the control system. The problems occur in the context of running/walking machines, or treadmills. However, the solutions may be applicable in any exercise apparatus where the speed (or force) of operation is determined by a motor, or motors, running under prestablished commands, as distinguished from exercise apparatus where the user-exerted energy controls the speed (or force) of operation, i.e., where the apparatus functions by resisting the user's energy. The resistance types of exercise apparatus include cycling machines, rowing machines, and the like.
In a running machine, or treadmill, a moving motor-driven belt determines the running, or walking, speed which the user must maintain in order to stay on the belt. A sudden undersired belt speed-up will throw the user off, with a risk of injury. Many such machines lack adequate safety protection against such a functional failure, with its inherent risks to the user.
The following describes an example of a potentially damaging event. In the apparatus, speed commands are entered and stored in a computer control system. Feedback representing actual speed is obtained from a sensor, such as a tachometer or an optical encoder. The motor speed control system compares the command and feedback signals, for the purpose of obtaining, and maintaining, the desired speed. If, for any reason, the feedback signal is lost, the automatic speed control system, if protective precautions are lacking, will "assume" that the belt has stopped; and therefore, power to the motor will be automatically and rapidly increased up to the maximum available. This would create a potentially dangerous runaway condition. Since the belt is moving toward the rear, its rapidly increasing speed can throw the user backward with a very powerful force.
The present invention is intended to provide much greater user protection than that previously incorporated in apparatus of the type under discussion.